Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
2001-08-06
2003-08-19
Walberg, Teresa (Department: 3742)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
C417S410500
Reexamination Certificate
active
06607367
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a scroll compressor, and more particularly, it relates to a scroll compressor improving sealability between a fixed scroll and a movable scroll and suppressing internal leakage.
BACKGROUND ART
A scroll compressor described in Japanese Patent Laying-Open No. 6-330864 (1994) is now described as an example of a conventional scroll compressor.
Referring to
FIG. 8
, a movable scroll
103
and a fixed scroll
102
are supported on an upper portion in a casing
101
of the scroll compressor. Movable scroll teeth
132
project from an end plate
131
of the movable scroll
103
. Fixed scroll teeth
122
project from an end plate
121
of the fixed scroll
102
. The movable scroll teeth
132
and the fixed scroll teeth
122
fit with each other thereby forming a compression chamber.
A suction port
180
for introducing refrigerant gas fed from a suction pipe
107
into the compression chamber is provided on the outer peripheral portion of the fixed scroll
102
. A discharge port
123
for discharging the refrigerant gas compressed to a high-pressure state is formed around the center of the fixed scroll
102
.
A motor
104
is provided on a lower portion in the casing
101
. A drive shaft
141
extending from the motor
104
is supported by a bearing housing
105
fixed to the lower portion of the movable scroll
103
. A boss
133
provided on the end plate
131
of the movable scroll
103
is engaged with an upper end portion of the drive shaft
141
.
A back pressure chamber
109
is formed between the bearing housing
105
and the movable scroll
103
. A high pressure (discharge pressure) acts on the back pressure chamber
109
. A seal ring
170
is provided between the movable scroll
103
and the bearing housing
105
.
This seal ring
170
seals the back pressure chamber
109
of a high pressure and a space of a low pressure (suction pressure) provided with the movable scroll
103
and the fixed scroll
102
. Therefore, it follows that the discharge pressure acts on a region of the back surface of the end plate
131
of the movable scroll
103
located inside the seal ring
170
and the suction pressure acts on another region of the back surface located outside the seal ring
170
.
The end plate
121
of the fixed scroll
102
is provided with a relief port
110
and a relief valve
111
for discharging the refrigerant gas from the compression chamber in the process of compression into a discharge chamber
101
A in order to prevent over-compression.
A cover body
124
covering the upper side of the discharge port
123
is mounted on the fixed scroll
102
with fixing bolts. The cover body
124
is coupled to a support plate
106
fixed to the upper portion in the casing
101
. The support plate
106
is provided with a communication hole
161
communicating with the discharge port
123
.
A communication path
101
C connects the discharge chamber
101
A of the casing
101
communicating with the communication hole
161
with a space
101
B located below the bearing housing
105
. The space
101
B communicates with a discharge pipe
108
for discharging the refrigerant gas of a high pressure from the casing
101
.
Operation of the aforementioned scroll compressor is now described.
Following rotation of the motor
104
, the movable scroll
103
revolves with respect to the fixed scroll
102
so that the compression chamber formed by the movable scroll teeth
132
and the fixed scroll teeth
122
spirally contractedly moves from the outer peripheral portion toward the central portion.
Thus, the refrigerant gas of a low pressure fed into the compression chamber from the suction pipe
107
through the suction port
180
is compressed to a high-pressure state. The high-pressure refrigerant gas is discharged from the discharge port
123
and flows into the space
101
B through the communication hole
161
, the discharge chamber
101
A and the communication path
101
C. The discharge pipe
108
discharges the refrigerant gas flowing into the space
101
B from the casing
101
.
The pressures acting on the end plate
131
of the movable scroll
103
in the aforementioned operations are now described. The pressure of the fluid in the compression chamber as well as a back surface pressure act on the end plate
131
.
FIG. 9
typically shows pressure distribution in the compression chamber and pressure distribution on the back surface with respect to positions of the end plate
131
.
As hereinabove described, the compression chamber spirally contractedly moves from the outer peripheral portion toward the central portion. Therefore, the pressure of the compression chamber increases from the outermost peripheral portion in a suction process toward a portion in a discharge process through a portion in the process of compression.
Therefore, the portion of the compression chamber in the suction process has the lowest pressure, i.e., a suction pressure Ps, and the portion in the discharge process has the highest pressure, i.e., a discharge pressure Pd. The portion of the compression chamber in the process of compression exhibits a pressure Pm between the suction pressure Ps and the discharge pressure Pd.
Thus, it follows that force (separating force) for separating the movable scroll
103
from the fixed scroll
102
acts on the end plate
131
of the movable scroll
103
on the basis of the aforementioned pressures.
On the other hand, the discharge pressure Pd acts on the region of the back surface of the end plate
131
located inside the seal ring
170
while the suction pressure Ps acts on the region located outside the seal ring
170
, as hereinabove described.
Thus, it follows that force (pressing force) for pressing the movable scroll
103
against the fixed scroll
102
acts on the end plate
131
of the movable scroll
103
oppositely to the separating force, on the basis of the aforementioned pressures.
When the scroll compressor is operated at a standard operating pressure ratio, the pressures are distributed as shown in FIG.
9
. In this case, therefore, sufficient pressing force is attained as compared with the separating force for preventing separation of the movable scroll
103
from the fixed scroll
102
. The scroll teeth
122
and
132
come into close contact with the end plates
121
and
131
respectively, to be capable of suppressing internal leakage.
The operating pressure ratio, depending on a refrigerating cycle of the scroll compressor including an evaporator and a condenser, is obtained by dividing the discharge pressure Pd depending on a condensing pressure by the suction pressure Ps depending on an evaporating pressure.
At the standard operating pressure ratio, this value is at the same level as a designed pressure level decided by the scroll teeth
122
and
132
, more specifically in the range of about 2 to 5.
As hereinabove described, sufficient pressing force is attained as compared with the separating force to be capable of suppressing internal leakage when the scroll compressor is operated at the standard operating pressure ratio.
When the scroll compressor is operated at a low operating pressure ratio of not more than about 2, however, the following problem arises: Such an operating pressure ratio is less than the designed pressure ratio. More specifically, the suction pressure Ps is relatively increased as compared with the discharge pressure Ps or the discharge pressure Pd is relatively reduced as compared with the suction pressure Ps at such an operating pressure ratio. In this case, therefore, the pressure of the compression chamber in the process of compression may exceed the reduced discharge pressure.
Pressure distribution in the compression chamber and pressure distribution on the back surface with respect to the positions of the end plate
131
with such a low operating pressure ratio are now described. As shown in
FIG. 10
, the portion of the compression chamber in the suction process exhibits the lowest pressure, i.e., the suction pressure Ps, while the portion in the process of compression exhibits the h
Ishiguro Suguru
Kajiwara Mikio
Kitaura Hiroshi
Shibamoto Yoshitaka
Burns Doane , Swecker, Mathis LLP
Daikin Industries Ltd.
Patel Vinod D
Walberg Teresa
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